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slooooow linking

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stahta01:

--- Quote from: wilcomir on October 31, 2009, 01:00:06 pm ---hi all!
here's what's produced when I write mingw32-g++ -v:

--- Code: ---C:\Documents and Settings\Vladi>mingw32-g++ -v
Reading specs from C:/Programmi/CodeBlocks/MinGW/bin/../lib/gcc/mingw32/3.4.5/sp
ecs
Configured with: ../gcc-3.4.5/configure --with-gcc --with-gnu-ld --with-gnu-as -
-host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --
enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shar
ed --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --ena
ble-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-sync
hronization --enable-libstdcxx-debug
Thread model: win32
gcc version 3.4.5 (mingw-vista special)
--- End code ---

and here's what I always compile & link:


--- Code: ---#include <iostream>
using namespace std;

int main () {
    cout << "insert a number";
    int n;
    cin >> n;
    cout << 2*n;
}

--- End code ---

the .o file is about 2kb, while the generated .exe is nearly 500kb

thanks!

--- End quote ---

Debugging and library code increases size.

Tim S.

wilcomir:

--- Quote from: stahta01 on October 31, 2009, 01:26:26 pm ---Debugging and library code increases size.

Tim S.

--- End quote ---

So what do you suggest?

thanks!

thomas:

--- Quote from: wilcomir on October 31, 2009, 01:00:06 pm ---the .o file is about 2kb, while the generated .exe is nearly 500kb
--- End quote ---
According to your commandline, you are not generating any symbols and not linking to any external libraries. Thus, a program with a 2 kB object file should have minimum PE size, i.e. 4 kB. If it doesn't, then maybe you have some malware on your computer which adds that code (possibly several ones, since 500 kB is quite a lot).

To be sure it really isn't just debug symbols, though, rename the prova.exe to something that doesn't look like a program, for example prova.txt.
Then run strip prova.txt. If the program is now about 4kB, all is good, then the increased size was only due to debug symbols. If it's still around 500 kB and it was really created from a 2 kB object file with a commandline as described above, then you may want to ring the alarm bells.

MortenMacFly:

--- Quote from: thomas on November 03, 2009, 12:48:27 pm ---
--- Quote from: wilcomir on October 31, 2009, 01:00:06 pm ---the .o file is about 2kb, while the generated .exe is nearly 500kb
--- End quote ---
Then run strip prova.txt. If the program is now about 4kB, all is good, then the increased size was only due to debug symbols. If it's still around 500 kB and it was really created from a 2 kB object file with a commandline as described above, then you may want to ring the alarm bells.

--- End quote ---
Same here. I am using TDM's GCC 4.4.1(2). The file is as described, not linked against any additional libs (at least that's my purpose).
-> After compilation / linking: ~ 980 kB
-> After strip: ~500 kB.
Same thing with GCC 3.4.5:
-> After compilation / linking: ~ 500 kB
-> After strip: ~280 kB.

However - looking at was the linker accesses I see:
- crtbegin.o / crtend.o
- crt2.o
- libstdc++.a
- libmingw32.a
- libgcc.a
- libmoldname.a
- libmingwex.a
- libmsvcrt.a
- libuser32.a
- libkernel32.a
...which are all quite big in size.
If I look at the symbols of the final stripped exe I see references to MSVCRT and others.

However - my computer is 100% virus free, the same applies in a VM without network connection.

So what...?! I have this feeling that this discussion will lead to nowhere.

thomas:
Surprising. Most of these should add nothing or next to nothing in my opinion, unless you really enforce it by using ultra-fat components of libstdc++. user32, kernel32, or msvcrt for example will only add some thunks for functions that your program actually uses, that's a few bytes for a small program (8 bytes per thunk unless you force alignment to be more than that), and maybe a kilobyte or two top for pretty much every program. libstdc++ can certainly add a few hundred kilobytes, but only if you actually use the stuff (and then it's not surprising).

I've just looked what the unit test program to one of my containers compiles to, as that's pretty much the smallest non-helloworld project I have at hand. Gcc 4.4.0-tdm turns roughly 10 kB of sources (not counting system headers) into a 8.5 kB object file, and this into a 33 kB executable. That includes around 7 kB for the main program using std::vector, and 1 kB for exception handling. It takes well under a second to compile and link. Gcc 4.4.1-tdm produces considerably larger executables, though I don't have it installed now, so can't tell for this example.

Well, whichever it is, you're probably right insofar as we'll not likely be able to tell why wilcomir's executables are that big.

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